CompilerInvocation::GetResourcesPath

[owinebar]

I tried to build tool-template.cpp in an out-of-tree project directory based on a recent main checkout (version 18 at this time). I compiled and installed all the llvm projects from this checkout in ${HOME}/dev, including the shared libraries.
The CMakeLists.txt in the out-of-tree project is set to link tool-template to the shared libraries in ${HOME}/dev. tool-template successfully builds, but raises an error when the resulting binary is run on its source.
As alluded to at the end of https://clang.llvm.org/docs/LibTooling.html, the problem is that the resource directory is set relative to the executable in CompilerInvocation::GetResourcesPath. If I move the tool-template executable to ${HOME}/dev/bin, for example, it processes its source with no issue.

It would make more sense, if the executable is dynamically linked to libclang, to determine the resources path relative to the location of libclang.so.

[owinebar]

I should also note that if I specify "-resource-dir" as an argument in the compilation database of the out-of-tree build to point to ${HOME}/dev/lib/clang/18, the out-of-tree tool-template build runs without error.

I understand why libTooling would prefer to reference the resource directory associated with the tool rather than the compiler specified in the compilation database, but this seems somewhat inconsistent. It would make more sense to me, consistency-wise, to either default to ignoring the resource-dir option in the command-line and accepting such an option for the tooling, similar to -p, or to default to using the resource directory associated with the compiler specified in the compilation database.

This might be a distinct issue.

[owinebar]

For now, I'm using a workaround of explicitly specifying the resource directory based on the path of libclang.so if it is dynamically linked, or the executable if not. The following appears to work on my linux system.

using namespace llvm;

namespace clang {
namespace tooling {
std::string getClangPath(const char *argv0, void *MainAddr) {
    Dl_info libclang_info{};
    void *libclang = dlopen("libclang.so",RTLD_LAZY);
    if (libclang) {
        // use a symbol defined since the inception of the library
        void *spcl = dlsym(libclang,"clang_createTranslationUnit");
        int check = dladdr(spcl,&libclang_info);
        dlclose(libclang);
        if (check && libclang_info.dli_fname) {
            char real_path[PATH_MAX];
            if (realpath(libclang_info.dli_fname, real_path))
                return std::string(real_path);
        }
    }
    // Fall back to path of the executable if libclang is not dynamically linked
    std::string exe_path = llvm::sys::fs::getMainExecutable(argv0,MainAddr);
    return exe_path;
}
}
}